<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    while (true) {

      let i = prompt("请输入您需要的星期")
      switch (i) {
        case "星期一":
          document.write("monday")
          break
        case "星期二":
          document.write("tuesday")
          break
        case "星期三":
          document.write("Wednesday")
          break
        case "星期四":
          document.write("Thursday")
          break
        case "星期五":
          document.write("Friday")
          break
        case "星期六":
          document.write("Saturday")
          break
        case "星期日":
          document.write("Sunday")
          break
        default:
          break
      }
      if (i === "退出") {
        alert("退出成功！")
        break
      }
    }
  </script>
</body>

</html>